The present invention relates to display systems which display a video by modulating and scanning a light beam from a coherent light source such as a laser light source in accordance with video signals, and relates to techniques to reduce speckle noises at the time of display.
A laser display system is proposed in JP-A-2003-021800, for example, in which a video is displayed on a screen by emitting three color laser beams to an operating mirror and reflecting the three color laser beams. In such a laser display system, the use of the high coherent laser beam causes a speckle phenomenon that a random spotted pattern is generated, and thus the quality as a display becomes an issue.
In order to suppress such speckle phenomenon, there is a method of mechanically vibrating an optical path as shown in JP-B-4144713, for example, however, the frequency is insufficient for sufficiently reducing the speckle and thus the speckle reduction effect is small.
As the other display systems using the laser beam, a method is also proposed as shown in JP-A-06-208089, in which an image modulated by an optical modulator is enlarged and projected in accordance with image information. This method also has a problem of the speckle. With regard to this problem, JP-A-2007-163702 proposes a speckle canceller comprising a pair of transparent substrates and a liquid crystal sealed therebetween.